You'll have to remake the whole game almost from scratch to fix it. Empty ubisoft-like open world filled with checklist crap, braindead combat, shitty RPG system with level-scaled enemies, shitty itemization, downgraded alchemy, poor enemy variety, etc etc. Witcher 3 succeeded only because of writing and production qualities.
Pretty much all the points i have quoted above and even writing is copy-paste(Witcher's contracts, Treasure quests for exemple)
That's why i said that Witcher 3 needed to be entirely overhauled.
Here is a quick exemple of i'm saying.
Let's compare the Father Gascoigne (First Boss in Bloodborne) vs The Chief of the Wild Hunt(the last boss in Witcher 3)
When Father Gascoigne uses his axe in one Hand he can:
Single attack you with his axe.
Attack while jumping.
dodges and attack
rolls and then attack.
He scrapes the ground with his axe and then attck you with it.
Does a concentrate attack on you to do more damage
Uses his pistol to destabilize you.
When father Gascoigne uses his axe in one two hand:
Does a thrust attack with his axe
Does a concentrate attack
uses his pistol while using his axe in two hand.
Does a single attack
When father Gascoigne is in Beast mode:
Claw attacks
High kick attacks
Attacks from above
Uses all of this strength to do a strong powerfull attack with his claws
Father Gascoigne has
14 DIFFERENTS TYPES OF ATTACKS.
Now Witcher's last boss:
Can do a single attack.
Can teleport.
Can do a magic attack
He can parries.
Can destabilizes you with his legs.
Eredin Has
5 differents types of attacks
Here is the proof.Needed twice as much work to be a powerfull smart boss